Luminaires, i.e., illumination devices have been proposed which include a panel-like light guide plate made from optically transmissive material. The illumination devices proposed causes a pattern to be shown in accordance with the direction light enters the light guide plate (for instance, Japanese Patent Publication No. 2003-519810).
The illumination device disclosed in JP 2003-519810A includes an optically transmissive panel. The panel is arranged between a light output window, and a rear wall facing the light output window, and includes optically transmissive first and second end surfaces that are arranged at mutually different locations. Light entering the panel from a light source facing the first end surface is reflected by the plurality of rectangular prisms aligned along a first light symbol formed on the rear wall. The light then exits from a light output surface causing a first light symbol to be shown. Light entering the panel from a light source facing the second end surface is reflected by the plurality of rectangular prisms aligned along a second light symbol formed on the rear wall. The light then exits from a light output surface causing a second light symbol to be shown. Alternating which light source is turned on in this illumination device changes the pattern presented.